Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Derivative Problems, Please help!

  1. Sep 21, 2004 #1
    Hey, I am having some trouble solving this problem..soon as i see how it works i just know i gunna go "Ooh, thats all i had to do" Here it is:

    A shrinking lollipop. A shperical Tootsie Roll Pop that you are enjoying is giving up volume at a steady rate of 0.08 mL/min. How fast will the radius be decreasing when the Tootsie Roll Pop is 20 mm across?

    Ok, I know I need to take the derivative of V=(4/3)pi(r^3) i just get lost in that proccess...please help..

    THank you very much
  2. jcsd
  3. Sep 21, 2004 #2


    User Avatar
    Homework Helper

    They are asking you for [tex] \frac{dr}{dt} [/tex]

    Why don't you differiantiate with respect to t?.
  4. Sep 21, 2004 #3


    User Avatar
    Homework Helper

    Show me your derivative, so i can see where it went wrong.
  5. Sep 21, 2004 #4


    User Avatar
    Science Advisor
    Homework Helper

    you need to use the chain rule, dV/dt = (dV/dr) (dr/dt)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook